Infiltration cannula

ABSTRACT

An infiltration cannula and method of using the infiltration cannula during an infiltration procedure are disclosed herein. The infiltration cannula has a flexible cannula and a hub. The cannula has a proximal end and a distal end. The cannula also has a plurality of apertures disposed in a pattern about the distal end. The apertures are configured to infiltrate fluid into the subcutaneous or muscle tissue of a patient. The hub is configured to be held by a person performing the infiltration procedure. The hub has a first end and an opposing second end. The first end is attached to the proximal end of the flexible cannula and the second end includes a connector configured to connect to an input source for receiving the fluid to be infiltrated into the subcutaneous tissue of the patient. The fluid flows from the connector, through the hub and into the cannula.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application is a continuation-in-part application ofApplicant's pending U. S. Ser. No. 10/442,370 filed May 21, 2003entitled INFILTRATION CANNULA, and is related to Applicant's pendingapplication serial number unknown, filed concurrently herewith entitledDRUG SYSTEM FOR ACCELERATED SUBCUTANEOUS ABSORPTION, the disclosures ofwhich are expressly incorporated herein by reference.

STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT

[0002] Not Applicable

BACKGROUND OF THE INVENTION

[0003] Definitions:

[0004] Tumescent Technique: The tumescent technique is a method ofsubcutaneous drug delivery of large volumes of very dilute medicationtogether with dilute epinephrine in isotonic solution of crystalloidinfiltrated directly into subcutaneous fat or muscle to produce swellingand firmness, or tumescence, of the targeted tissues, and thus producevery slow systemic absorption as a result of intense subcutaneousvasoconstriction.

[0005] Tumescent Drug Delivery: Tumescent drug delivery refers to thetumescent technique for delivering a drug into the subcutaneous space.Drugs other than lidocaine can be administered by means of tumescentdelivery, that is, by subcutaneous infiltration of extremely dilutedrug, with or without epinephrine as a vasoconstrictor.

[0006] Tumescent Local Anesthesia (TLA) is local anesthesia produced bydirect infiltration into subcutaneous tissue of large volumes of verydilute lidocaine and epinephrine in a crystaloid solution such asphysiologic saline (NaCl) or lactated Ringer's solution.

[0007] Tumescent Local Anesthetic Solution (TLA Solution) is the localanesthetic solution used to produce TLA. Typically, a TLA Solutionconsists of a 10to 20 fold dilution of commercially availableconcentration of lidocaine and epinephrine. Thus, a commercial solutionof lidocaine and epinephrine contains 10grams of lidocaine per liter (10gm/L) and 10 milligrams of epinephrine per liter. In contrast TLASolution typically contains less than 1gm/L lidocaine and epinephrine(1mg/L). Typically the volume of infiltrated TLA Solution is so largethat the skin and subcutaneous tissue becomes tumescent, in other wordsswollen and firm.

[0008] The present invention relates in general to cannulas and inparticular to an infiltration cannula that allows for intermittentinfiltration of fluids, such as a local anesthetic.

[0009] Many medical procedures require infiltration of fluids, such as alocal anesthetic. One method of infiltration of local anesthetic is viaan infiltration cannula. Infiltrators are known as sprinkler-tip orKlein™ (the present applicant) needle infiltrators. These cannulas areconstructed out of a rigid stainless steel and have one or moreapertures, which are typically round or oval, and are distributed aboutthe distal end of the cannula. The apertures are distributed over about15% to 25% or less than 5.0 cm of the distal end of the cannula needle.These traditional infiltration cannulas are intended to be insertedthrough a small incision in the patient's skin and then moved in and outthrough the subcutaneous tissue while a dilute solution of localanesthetic (or other pharmaceutical solution) is ejected through thedistal apertures. Such infiltrators typically have a blunt tip andrequire the placement of a small hole (made by a one mm skin-biopsypunch or a small surgical blade) through which the blunt tipped cannulacan be passed. The piston-like in and out motion of the cannula causesthe patient discomfort.

[0010] Another method of fluid insertion is via a peripherally insertedcentral catheter, also called a PICC line comprising an elongate plastictube that is placed inside a vein of the patient. PICC lines aretypically used for procedures requiring delivery of fluids over aprolonged period of time. For example, a PICC line may be used when apatient needs to receive intravenous (IV) fluids, such as medication ornutrients over a prolonged period of time, such as a week or more.

[0011] The On-Q® Pain Management System marketed by I-Flow® Corporationemploys a PICC line type system for continuously providing localanesthetic. This system provides prolonged local anesthesia by means ofan elastomer (elastic container) device that continuously infiltrates asolution of local anesthesia over many hours. The On-Q® device comprisesa long soft flexible tube with many small holes arranged along asignificant portion of the tube. The On-Q® device is designed to beinitially positioned within a surgical wound at the time of surgery.After the surgical wound is closed, the On-Q® device permits slow steadyinfiltration of a local anesthetic solution into the wound, therebyattenuating post-operative pain. The On-Q® device cannot be insertedthrough a tiny hole in the skin into subcutaneous tissue. Thus there isa need for a simple device that can permit the direct percutaneousinsertion of a multi-holed infiltration cannula into subcutaneous tissuefor the localized delivery of medications such as local anesthetics,chemotherapeutic agents, or crystalloids for parenteral hydration.

[0012] Traditional techniques for subcutaneous injection of localanesthetic solutions use a high-concentration/low-volume of localanesthetic. This is associated with a rapid systemic absorption of thelocal anesthetic. In order to achieve a prolonged local anestheticeffect, the traditional techniques for using local anestheticsnecessitate either frequent repeated injections or slow continuoussubcutaneous infusion of the local anesthetic. As described above,repeated injections or piston-like movement of the cannula causespatient discomfort. Slow continuous infiltration may not be desirable incertain situations. Furthermore, continuous infiltrations restrictpatient movement for extended periods of time which also cause thepatient discomfort. Thus, there is a need for a system for infiltrationof a local anesthetic into subcutaneous tissue which decreases patientdiscomfort, and allows prolonged local anesthesia either by rapid bolusinjections or continuous slow infiltration. Furthermore there is a needfor a devise that can provide pre-emptive local anesthesia before asurgical wound is created. There is also a need for apercutaneously-insertable infiltration cannula, with applications thatare unrelated to the delivery of local anesthesia, which can be easilyinserted by rescuers with minimal clinical skill or training. Oneexample is the need for a cannula that permits emergency fluidresuscitation in situations where an IV cannot be established such asnighttime military combat conditions where using a flash light toestablish an IV access would be extremely dangerous. Another example isthe need to provide emergency fluid resuscitation to large numbers ofpatients in acute epidemic diarrhea (dehydration) associated withbiological warfare, or mass-trauma situations such as a natural disaster(earth quake) or terrorist attack. There is also a need for a devicethat can easily provide localized fluid resuscitation to bum victimswhereby fluid is infiltrated into the subcutaneous tissue directlysubjacent to burned skin.

BRIEF SUMMARY OF THE INVENTION

[0013] The present invention comprises an infiltration cannula andmethod of using the infiltration cannula during an infiltrationprocedure. The infiltration cannula preferably includes: a flexiblecannula, a hub, and a rigid stylet. The flexible cannula has a proximalend and a distal end. The flexible cannula also has a plurality ofapertures disposed in a pattern about the distal end. The apertures areconfigured to infiltrate fluid into the subcutaneous tissue of apatient. The hub is configured to be held by a person performing theinfiltration procedure. The hub has a first end and an opposing secondend. The first end is attached to the proximal end of the flexiblecannula and the second end includes a connector configured to connect toan input source for receiving the fluid to be infiltrated into thesubcutaneous tissue of the patient. The fluid flows from the connector,through the hub and into the flexible cannula.

[0014] The flexile cannula may be manufactured of plastic and the rigidstylet may be fabricated from stainless metal or rigid plastic. Thedistal end of the cannula is closed to cover the tip of the rigid styletor open with a hole allowing the tip of the rigid stylet to protrudethrough. The tip of the rigid stylet is either sharp to directly insertthrough the skin of the patient, or so blunt that a skin incision isrequired to permit insertion of the rigid stylet and the cannula intothe subcutaneous space. The stylet may be formed to have either a solidor hollow cross-sectional configuration.

[0015] The apertures may be arranged in a helical pattern or in a spiralpattern.

[0016] The apertures may be distributed over about 33% to about 90% ofthe distal end of the tubular needle.

[0017] The apertures may be round or oval. The size of the aperturesneed not necessarily be equal.

[0018] The fluid may comprise a local anesthetic or any othertherapeutic solution.

[0019] The infiltration procedure may be performed in conjunction withconventional medical procedures such as liposuction, but additionallymay simply be used as a mode of systemic drug delivery, or systemicfluid replacement therapy.

[0020] A method of infiltrating fluid into subcutaneous tissue of apatient using an infiltration cannula, such as the one described abovemay include the following steps.

[0021] A rigid stylet is inserted through a flexible infiltrationcannula. The infiltration cannula is inserted through a patient's skinand into the subcutaneous tissue or muscle tissue of the patient at adesired site with the stylet serving as a guiding wire. After the styletlet is withdrawn from the cannula, a fluid is provided from a fluidsource via the connector. The fluid is transported from the connectorthrough the hub and into the flexible cannula. The fluid is ejected fromthe cannula into the subcutaneous tissue or muscle of the patient viathe apertures.

[0022] The infiltration cannula used in performing the method preferablyincludes a connector for receiving the fluid from a fluid source, a hubin communication with the connector and a flexible cannula incommunication with the hub. The tubular needle has a plurality ofapertures disposed in a pattern about a distal end. The apertures areconfigured to infiltrate the fluid into the subcutaneous tissue ormuscle of the patient.

[0023] The above steps may be repeated intermittently, at intervalsbetween a few minutes to many hours.

[0024] After the desired amount of fluid has been infiltrated at a givensite, the infiltration cannula may be removed or may remain in place forpossible additional infiltration.

[0025] The infiltration cannula may additionally be inserted at a newsite.

[0026] Multiple infiltration cannulas (e.g., two) may be usedsimultaneously. Use of multiple infiltration cannulas preventsdisruption of the infiltration process when one infiltration cannula isremoved. Multiple infiltrators can be simultaneously inserted intoseparate areas to facilitate more rapid delivery of fluids.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] These as well as other features of the present invention willbecome more apparent upon reference to the drawings wherein:

[0028]FIG. 1 is a side elevation view of a stainless steel infiltrationcannula with a closed tip shown inserted in subcutaneous tissue shown inpartial cross section;

[0029]FIG. 2 is a section view of the infiltration cannula shown in FIG.1;

[0030]FIG. 3 is a side elevation view of a plastic infiltration cannulawith a closed tip shown inserted in subcutaneous tissue shown in partialcross section;

[0031]FIG. 4 is an exploded view of the infiltration cannula shown inFIG. 3;

[0032]FIG. 5 is a flow diagram illustrating an exemplary procedure forusing an infiltration cannula such as the one shown in FIG. 1 or the oneshown in FIG. 3; and

[0033]FIG. 6 is an exploded side elevation view of a plasticinfiltration cannula through which a stylet can be inserted.

DETAILED DESCRIPTION OF THE INVENTION

[0034] As described in further detail below, the present invention takesadvantage of the tumescent technique in order to provide intermittent orcontinuous, brief or prolonged infiltration of local anesthetic,physiologic fluid, antibiotics or other therapeutic solution. Thepresent invention results in a significant decrease in patientdiscomfort due to the elimination of the piston-like in and out motionof the cannula. Once the cannula is positioned in place, there is noneed to repeatedly move the cannula in and out through the tissue inorder to deliver the fluid to a wide area. Using the tumescent techniqueand stainless steel versions of the present invention, the time neededin order to complete the infiltration of a targeted anatomic area isreduced to nearly half of the time required when using traditional priorart cannulas. The device and method of the present invention can usemultiple (e.g., two or more) infiltration cannulas simultaneously. Whileone cannula is actively dispersing tumescent fluid into the subcutaneoustissue, the surgeon can reposition a second infiltration cannula. Thisallows the infiltration process to proceed without interruption, whereasprior art techniques of infiltration must be ceased each time thecannula is withdrawn from the skin and re-inserted into anotherdirection.

[0035] The flexible cannula version of the present invention provides ameans for relatively rapid fluid resuscitation in emergency situationssuch as when establishing an intravenous (IV) access is not feasible.The flexible cannula may have important applications as in treating awounded soldier in night-time combat conditions when establishing an IVaccess in total darkness is nearly impossible or using a flash lightmight attract enemy fire. The flexible cannula may similarly haveimportant applications in other areas of use such as treatingmass-casualty victims suffering hypovolemia as a result of epidemicinfections, biologic warfare, or trauma such as explosions, burns orradiation exposure. The flexible cannula similarly has applications insurgical patients wherein the surgeon can provide localizedpre-operative preemptive analgesia and simultaneously provide tumescentdelivery of a prophylactic dose of an antibiotic aimed precisely attissues targeted for surgical intervention.

[0036] As is well known, the tumescent technique was discovered byJeffrey Alan Klein, M.D. (the present applicant) in 1985. Dr. Kleinfirst published a description of the tumescent technique in 1987 when hedescribed the use of dilute lidocaine and epinephrine to permitliposuction totally by local anesthesia. The technique for tumescentlocal anesthesia is well known in dermatologic and plastic surgeryliterature. A detailed description of the tumescent technique has notbeen published in anesthesiology literature, and therefore, the uniquebenefits of the tumescent technique are not well recognized byanesthesiologists.

[0037] The tumescent technique comprises a drug delivery system thattakes advantage of a recently discovered reservoir effect of injecting arelatively large volume of relatively dilute solution of a drug into thesubcutaneous tissue.

[0038] The present invention takes advantage of the tumescent reservoirphenomenon for one of its important applications. After a large volumeof fluid containing dilute epinephrine is injected into subcutaneoustissue, the epinephrine-induced vasoconstriction dramatically slows thesystemic absorption of the fluid. In effect, this large volume ofsubcutaneous fluid behaves in a fashion that is analogous to thebehavior of a slow-release tablet in the stomach after oral ingestion.Although there is a relatively large total amount of drug in thepatients body, the drug is isolated from the systemic circulation by thefact that only the drug on the outer boundary of the mass of drug is theavailable for absorption, whereas the portion of the drug located withinthe central portion of the mass of fluid is virtually isolated from thesystemic circulation by virtue of profound capillary vasoconstriction.In contrast, when the tumescent fluid does not contain epinephrine thereis no clinically significant vasoconstriction after tumescentinfiltration, and the tumescent fluid is absorbed relatively rapidly.This has important clinical applications in situations where patientsare hypovolemic or dehydrated and unable to be given fluids by mouth orintravenously. The tumescent technique permits rapid systemic hydrationby direct subcutaneous or intramuscular injection of a large volume offluid through a multi-fenestrated infiltration cannula described in thisinvention.

[0039] There is a prior art technique known as hypodermoclysis wherein afluid is slowly and continuously infiltrated subcutaneously using a typeof steel hypodermic needle, known as a butterfly needle, having a singledistal aperture in order to provide fluid to patients who cannot begiven fluids by mouth and for whom an IV access cannot be established.Typically hypodermoclysis is used in the treatment of infants, or cancerpatients, in which IV access is not easily achieved. The technique ofhypodermoclysis is typically used to deliver relatively small volumes offluid, for example an adult might receive 70 ml per hour. At this smallhourly volume hypodermoclysis is not an efficient method for the rapidsystemic delivery of fluid in emergency situations that might requiretwo to four liters per hour. The reason is that when using a cannulawith only a single distal aperture, the local interstitial fluidpressure increases rapidly immediately adjacent to the single apertureas fluid infiltrates locally, which in turn dramatically slows the rateof subsequent fluid flow into the area. In contrast, the multipleapertures formed along the length of the cannula as described in thepresent invention, distribute the fluid throughout a much larger volumetissue before there can be a sufficient increase in the interstitialfluid to decrease the rate of additional infiltration. Further more, itis common practice to infiltrate the tumescent fluid into thesubcutaneous space under augmented external pressure provided by anexternal peristaltic pump specifically designed for tumescentinfiltration. By way of example and not limitation, a preferred suitableperistaltic infiltration pump is described in pending United Statespatent application Ser. No. 10/811,733, filed Mar. 29, 2004, entitledINFILTRATION PUMP HAVING INSULATED ROLLERS AND PROGRAMMABLE FOOT PEDAL,the disclosure of which is expressly incorporated herein by reference.

[0040] The peristaltic pump provides a sufficient degree of pressure toeasily overcome the localized increased interstitial pressure associatedwith the local effects of a tumescent infiltration. On the other hand,in situations where a peristaltic infiltration pump is not available,such as in remote locations without any available electrical power, thepresent invention still permits relatively rapid tumescent infiltrationby virtue of the multiple holes distributed along the length of theflexible cannula. Furthermore, external hydrostatic pressure can beapplied to the fluid flowing into the flexible cannula from the fluidreservoir by means of gravitational force derived from elevating thereservoir one to two meters above the patient. When using gravity toaugment the flow of tumescent fluid, the infiltration process can becontinuous or intermittent. In exemplary embodiments, the intermittentinjections are administered at intervals ranging from every few minutesto eight to twelve hours or more.

[0041] With the tumescent technique for local anesthesia, a large volumeof dilute solution of local anesthesia and epinephrine is injected intothe subcutaneous space resulting in a large bolus (or reservoir) ofsolution. The profound vasoconstrictive effect (shrinking of thecapillaries) caused by the dilute epinephrine, produces a dramatic delayin the systemic absorption of the local anesthetic, which prolongs theanesthetic effects of tumescent anesthesia for eight to sixteen timeslonger than traditional techniques.

[0042] Referring now to the drawings wherein the showings are forpurposes of illustrating preferred embodiments of the present inventiononly, and not for purposes of limiting the same, FIGS. 1 and 2illustrate a stainless steel (reusable) infiltration cannula 10 andFIGS. 3-4 and 6 illustrate a (single use) plastic infiltration cannula30. The cannula 10, 30 can be inserted under the skin 52 and into thesubcutaneous tissue 50 and tumescent local anesthesia can be infiltratedonce every eight to twelve hours.

[0043] Stainless steel infiltration cannulas 10, such as the one shownin FIGS. 1 and 2, are formed having precision high quality and arepreferably reusable. These cannulas can be used to provide tumescentlocal anesthesia for surgical procedures, such as liposuction, whichrequire tumescent local anesthesia over a relatively large area.

[0044] The cannula 10 includes a tubular needle portion 12 which has aproximal end 14 and a distal end 16. The proximal end 14 of the tubularneedle 12 is attached to a hub 20 that is used by the anesthesiologistor surgeon to grasp and hold the cannula 10 during the infiltrationprocedure. The hub 20 is connected to the tubular needle 12 at a firstend 22 and has a connector 24, such as a luer lock, at an opposingsecond end. The connector 24 is connected to a fluid source, such astubing connected to an IV bag. Fluid enters the cannula 10 via theconnector 24.

[0045] In exemplary embodiments, the tip at the distal end 16 is closed.The local anesthetic is infiltrated into the patient via apertures 18located proximate the distal end 16 of the tubular needle 12 of thecannula 10. In exemplary embodiments, the apertures 18 are disposedalong the distal end 16 of the cannula 10 in a spiral or helical patternand are distributed over the distal 33% to 90% of the tubular needle 12of the cannula 10. For example, if the length of the tubular needle D is15 cm and the apertures 18 at the distal end 16 cover a length dl of 5cm, the pattern of apertures of the cannula 10 are preferablydistributed over 33% of the tubular needle 12 of the cannula 10.

[0046] The proximal portion 14 of the cannula 10 is preferably devoid ofapertures in order to prevent fluid from leaking out of the cannulainsertion site in the skin.

[0047] Flexible plastic infiltration cannulas 30, such as the one shownin FIGS. 3, 4 and 6 are single use cannulas and can be used in one ofseveral unique ways. First, an anesthesiologist or surgeon can insert aninfiltration cannula 30 with stylet 46 into the subcutaneous tissue 50,remove the stylet 46, then attach an IV tubing to the infiltrator andinject tumescent local anesthesia into the targeted area withoutsubsequent repositioning of the infiltration cannula 30. The plasticflexible nature of the infiltration cannula 32 of the disposable plasticcannula 30 allows the patient to move or change position of the bodywithout risk of injury that might result if a patient moves while arigid steel cannula is inserted.

[0048] Preferably, the stylet 46 is formed of metal, e.g., stainlesssteel, or of a rigid plastic material. The plastic cannula 30 can beblunt-tipped with the metal stylet tip 48 covered by the rounded tip 39of the plastic cannula 30. Alternatively, the plastic cannula 30 can beopen-ended with the stylet 46 extending a short distance past the end 39of the plastic cannula 30 as shown in FIG. 6. In the case of the openended cannula, the stylet 46 can be either blunt-tipped (requiring askin incision to permit insertion into the subcutaneous space), orsharp-tipped (permitting the cannula to be inserted directly through theskin and into the subcutaneous space or muscle without requiring apreparatory skin incision). The sharp-tipped stylet can be formed ineither a solid or hollow cross-sectional configuration.

[0049] The plastic cannula shown in FIGS. 3 and 4 is similar to an IVcatheter except the sharp hollow stylet used for the insertion of an IVcatheter can be replaced by a solid obturator/stylet 46 that can beeither sharp or blunt tipped. Except for the removable stylet 46, theplastic cannula 30 is similar to the stainless steel cannula 10 shown inFIGS. 1 and 2 and described above. The plastic cannula 30 includes aflexible tubular needle 32 having a proximal end 34 and a distal end 36.The distal end has apertures 38 and the proximal end 34 is devoid ofapertures. As stated above, in exemplary embodiments, the pattern ofapertures 38 in the cannula 30 are distributed over the distal 33% to90% of the tubular needle 32 of the cannula 30. For example, if thetubular needle 32 of cannula 30 shown in FIGS. 3 and 4 has a length D of15 cm and the pattern of apertures are distributed over a length dl of13.5 cm, then the apertures 38 are distributed over 90% of the cannula.

[0050] A typical infiltration cannula 10, 30 may have a diameterequivalent to 20, 18, 16 or 14 gauge with small apertures 18, 38 placedevery 5mm along the cannula in a spiral or helical pattern. It will beappreciated that the dimensions used herein are exemplary and that thecannula dimensions, range of gauge, length of cannula, relative sizeshape and pattern of apertures can vary greatly depending upon clinicalpreference.

[0051] The proximal end 34 of the tubular needle 32 shown in FIGS. 3 and4 is attached to a hub 40 that is used by the anesthesiologist orsurgeon to hold the cannula 30 during the infiltration procedure. Thehub 40 is connected to the tubular needle 32 at a first end 42 and has aconnector 44 at an opposing second end. The connector 44 is connected toa fluid source. As described above and shown in FIG. 4, the stylet 46can be inserted and removed from the cannula 30.

[0052] Infiltration using a plastic infiltration cannula 30, such as theone shown in FIGS. 3 and 4, can be accomplished using an infiltrationpump. Alternatively, the force of gravity could be used to push thetumescent fluid into the tissues by hanging a reservoir plastic bag oftumescent local anesthesia (or other dilute drug, such as achemotherapeutic agent or antibiotics) on an IV pole and connecting bagto the infiltration cannula by an IV line.

[0053] Another application is the injection of tumescent localanesthesia into a localized area through which a surgeon plans to make asurgical incision. The effects of vasoconstriction, resulting from theepinephrine in the tumescent local anesthetic solution, within thetumesced tissue minimizes surgical bleeding. In a uniquely preemptivefashion, the present invention can produce, via the pre-operativeinfiltration of tumescent local anesthesia, prolonged post operativeanalgesia and also preemptively reduce the risk of surgical woundinfections resulting from the bacteriacidal effects of lidocaine.

[0054] Yet another application is to provide an easily accessible routefor systemic administration of crystalloid fluids/electrolytes forsystemic hydration or for other types of drug therapy. Potentialclinical applications include emergency resuscitation with systemicfluids in situations where insertion of an IV catheter into a veincannot be readily achieved. Examples of situations where emergencyaccess for intravenous delivery of fluids might not be possible includeacute trauma or burn wound in civilian or military situations. Anotherapplication may be the emergency treatment of dehydration associatedwith prolonged vomiting or diarrhea as a result of chemical warfare orbiological warfare (e.g., epidemic cholera among pediatric patients inrural third world settings). A subcutaneous infiltration catheter caneasily be introduced by a layman, whereas inserting an IV catheter intoa vein of a patient that is severely dehydrated can be difficult evenfor a skilled physician. Delivery of systemic fluids by subcutaneousinfiltration is safer in a zero gravity situation (for example, theSpace Station). The addition of a small amount of capillary vasodilator(e.g., methylnicotinamide) to the subcutaneous fluid can be used toaccelerate the systemic absorption of the fluid or drug into theintravascular space. Further applicational uses for the presentinvention are described in co-pending application serial number unknown,filed concurrently herewith entitled DRUG DELIVERY SYSTEM FORACCELLERATED SUBCUTANEOUS ABSORPTION, the disclosure of which isexpressly incorporated herein by reference.

[0055] The cannula 10, 30 is intended to be inserted far enough throughthe skin 52 so that all of the apertures 18, 38 are within the fat 50 ormuscle of the patient. Once the cannula 10, 30 is properly positioned,it can remain stationary while the local anesthetic (or otherpharmaceutical) solution is injected.

[0056] After one portion of the targeted area has been tumesced, theinfiltration is briefly terminated (either by turning off the pump or byclamping the IV tubing) while the cannula 10, 30 is repositioned intoanother area of the subcutaneous tissue. The infiltration is thenrestarted with the cannula stationary in its new position.

[0057] The infiltrator 10, 30 can also be used in the traditional modewhereby the cannula 10, 30 is moved through the targeted tissue whilethe fluid is simultaneously pumped through the cannula 10, 30 and intothe subcutaneous tissue 50.

[0058] Another unique aspect of the tumescent technique's reservoireffect is that one can conveniently achieve a long, slow, steadyabsorption of a drug delivered to the subcutaneous space 50 usingperiodic injections of a tumescent solution. In certain situations,using a slow IV infusion, the alternative technique, can achieve a slowsystemic absorption of a drug but may be difficult, require greaterclinical expertise, be more expensive, and therefore, less practicalthan the technique described herein.

[0059]FIG. 5 is a flow diagram illustrating steps performed in anexemplary infiltration procedure using a cannula 10, 30 such as the oneshown in FIGS. 1 and 2 or the one shown in FIGS. 3 and 4, respectively.The procedure begins by inserting the tubular needle 12, 32 of theinfiltration cannula 10, 30 into a desired subcutaneous tissue site 50,e.g., via an incision in the patient's skin 52 (block 100). Fluid isthen transported from the fluid source (e.g., an IV bag) into thecannula 10, 30 via the connector 24, 44 that is connected to the fluidsource. The fluid is transported from the connector 24, 44 through thehub 20, 40 and into the tubular needle 12, 32 (block 102). The fluid isthen ejected from the cannula 10, 30 into the subcutaneous tissue 50 ofthe patient via the apertures 18, 38 at the distal end 16, 36 of thetubular needle 12, 34 of the cannula 10, 30 (block 104).

[0060] The fluid is transported (block 102) and ejected (block 104)until infiltration at the current site is completed (yes in decisionblock 106). The fluid can be injected into multiple sites in order todistribute the solution over a greater area.

[0061] Infiltration at a particular site may be deemed complete uponemptying of the fluid source or based on the anesthesiologist orsurgeon's decision to stop the infiltration at the current site. Afterone portion of the targeted area has been tumesced, the infiltration canbe briefly terminated (either by turning off the pump or by clamping theIV tubing) while the cannula 10, 30 is repositioned into another area ofthe subcutaneous tissue. The infiltration may then be restarted with thecannula stationary in its new position. If the infiltration at a site iscomplete (yes in decision block 106), the cannula is removed from thecurrent site (block 108). If the infiltration at the current site is notcomplete (no in decision block 106), fluid is transported from the fluidsource (block 102) and ejected into the subcutaneous tissue (block 104)until infiltration at the site is complete (yes in decision block 106).

[0062] If infiltration is complete at the current site (yes in decisionblock 106) but infiltration is not complete (no in decision block 110),the tubular needle 12, 32 of the infiltration cannula 10, 30 is insertedinto a new area of subcutaneous tissue 50. The process described aboveis performed until the infiltration process is complete (yes in decisionblock 110). This process can be continuous or repeated intermittently.

[0063] As described above, multiple infiltration cannulas (e.g., can beused at once). Thus, a second or additional cannulas can be inserted(block 100) at the same time as a first cannula is being removed (block108). Thus, the infiltration process need not be interrupted in order toreposition a single cannula.

[0064] Additional modifications and improvements of the presentinvention may also be apparent to those of ordinary skill in the art.Thus, the particular combination of parts described and illustratedherein is intended to represent only a certain embodiment of the presentinvention, and is not intended to serve as a limitation of alternativedevices within the spirit and scope of the invention.

What is claimed is:
 1. An infiltration cannula for use in aninfiltration procedure, the infiltration cannula comprising: a flexibletubular needle comprising: a proximal end; a distal end; and a pluralityof apertures disposed in a pattern about the distal end, the tubularneedle sized to receive a rigid stylet therein, and the aperturesconfigured to infiltrate fluid into subcutaneous tissue or muscle of apatient; and a hub configured to be held by a person performing theinfiltration procedure, the hub having a first end and an opposingsecond end, the first end being attached to the proximal end of thetubular needle, the second end comprising a connector configured toconnect to an input source for receiving the fluid to be infiltratedinto the subcutaneous tissue of the patient, the fluid flowing from theconnector, through the hub and into the cannula
 2. The infiltrationcannula as recited in claim 1, wherein the flexible material comprisesplastic.
 3. The infiltration cannula as recited in claim 1, wherein thedistal end of the cannula is closed to cover the tip of the stylet. 4.The infiltration cannula as recited in claim 1, wherein the distal endof the cannula is open with a hole allowing a tip of the rigid stylet toprotrude through.
 5. The infiltration cannula as recited in claim 4,where in the tip of the rigid stylet is sharp enough to directly insertthrough the skin of the patient.
 6. The infiltration cannula as recitedin claim 1, wherein the rigid stylet is blunt tipped.
 7. Theinfiltration cannula as recited in claim 1, wherein the rigid stylet isfabricated from stainless metal or rigid plastic.
 8. The infiltrationcannula as recited in claim 1, wherein the apertures are arranged in ahelical pattern.
 9. The infiltration cannula as recited in claim 1,wherein the apertures are arranged in a spiral pattern.
 10. Theinfiltration cannula as recited in claim 1, wherein the apertures aredistributed over about 33% to about 90% of the distal end of the tubularneedle.
 11. The infiltration cannula as recited in claim 1, wherein theapertures are round.
 12. The infiltration cannula as recited in claim 1,wherein the apertures are oval.
 13. The infiltration cannula as recitedin claim 1, wherein the fluid is a therapeutic solution.
 14. Theinfiltration cannula as recited in claim 13, wherein the infiltrationprocedure is performed in conjunction a surgical procedure involving anincision through the skin.
 15. The infiltration cannula as recited inclaim 13 wherein the infiltration procedure is performed simply todeliver a therapeutic solution using a tumescent-like technique.
 16. Amethod of infiltrating fluid into subcutaneous tissue of a patient, themethod comprising: (a) inserting an infiltration cannula through apatient's skin and into the subcutaneous tissue of the patient at adesired site, the infiltration cannula comprising a connector forreceiving the fluid from a fluid source, a hub in communication with theconnector and a tubular needle in communication with the hub, thetubular needle having a plurality of apertures disposed in a patternabout a distal end, the apertures configured to infiltrate the fluidinto the subcutaneous the tissue of the patient; (b) receiving fluidfrom the fluid source via the connector; (c) transporting the fluid fromthe connector through the hub and into the tubular needle; and (d)ejecting the fluid from the tubular needle into the subcutaneous tissueof the patient via the apertures.
 17. The method recited in claim 16,further comprising repeating steps (a)-(d).
 18. The method recited inclaim 17, wherein steps (a)-(d) are repeated at intervals that varybetween minutes to many hours.
 19. The method recited in claim 16,comprising the further step of removing the infiltration cannula. 20.The method recited in claim 19, further comprising inserting theinfiltration cannula at a new site in the patient's skin.
 21. The methodrecited in claim 20, wherein at least two infiltration cannulas areinserted into the patient's skin to prevent disruption of the methodwhen one infiltration cannula is removed.
 22. The method recited inclaim 16, wherein the fluid is a local anesthesia.
 23. The methodrecited in claim 22, wherein the method is performed in conjunction witha surgical procedure or therapeutic drug delivery.